Iseria Queen (Star Ocean 2)

The Iseria Queen is one of the two final superbosses in Star Ocean: The Second Story and its PSP port, Star Ocean: Second Evolution (the other being Gabriel Unlimited). She can be fought by playing The Devil's Aria by a character who has Level 10 Music and the Listening and Rhythm Sense talents. She is easily the strongest enemy in the game in terms of statistics.

Strategy

1) Keep everyone out of harms way and attack her using long range attacks such as Opera, magic, and Ashton's Tri-Ace. This is not recommended since it takes a really long time but is safe strategy.

2) Have a party full of fighters that have enough HIT so they don't get parried and countered. Continously attack her with everything so that she is continously flinching and have little room to retaliate. Using the Combat Skill Back-Attack is helpful to prevent the fighters from facing Iseria directly, as a parry or counter attack can be really deadly. Heal and raise if necessary. Claude's Eternal Sphere and accessories such as Slayer Ring greatly helps. Dias equipped with Crimson Diablos and Back-Attack is capable of stunlocking Iseria using his Illusion Killer Move (max profiency).

The same strategy also works on Gabriel Unlimited. Gabriel has less AVD and HP but letting him get a spell off can lead to a party wipe.

3) Have everyone equip a Bloody Armor. This makes them invulnerable but will drain their health over time. Have Rena cast Fairy Heal whenever their health drops below 3000. This is essentially a gurantee win and is considered by many to be cheating.

4) Have Rena or Celine continuously cast Light Cross or Ray. It is recommended to choose only one of them since these spells are weak, but they have fast casting, which will greatly help in keeping the Queen at bay.

This works even better on Gabriel Unlimited due to the fact that he has far less HP and that it will keep him from casting his powerful spells.

5) The best and fastest stragegy requires the Angel Armband and Ashton. Due to his fast attacks and the star spray ability of the Angel Armband, Ashton can keep the Queen indefinitely stun-lock if he doesn't get parry a lot (Foot Symbol helps here if you're level is too low). Works well in combination with strategy 2 and 4, with the Laventine Sword and Slayer Ring equipped (as the extra hits will maximize the efficiency of the stunlocks).

Works even better on Gabriel Unlimited due to his much lower HP, just makes sure to have Rena or Celine cast Light Cross or Ray to stop his potential initial Earthquake or to stop him if he slips free. Having EARTH absorb also works. If you somehow have trouble keeping the bosses stun-lock because you can't press the attack button faste enough (especally Gabriel since he is really dangerous if left alone), abuse strategy 4 and it should be fine even if it is a bit tedious.

The downside to this strategy is that you must have the Angel Armband, which means you must have defeated the Iseria Queen at least once already.